Technical Field
The present invention relates to a detector for liquid chromatography and a method to correct a detection signal thereof.
Background Art
In general-purpose liquid analyzers including a liquid chromatograph, absorbance detectors have been widely used because of its high detection sensitivity and user-friendliness. Especially an ultraviolet wavelength band that is short wavelengths of 300 nm or less includes excitation wavelengths of various functional groups in organic compounds, and so all industrially-useful organic compounds can be a detection target in such a wavelength band. Specifically transitions of σ→σ*, n→σ*, n→π* and π→σ* correspond to electron transitions in this wavelength region, in which hydroxyl groups, carboxyl groups, carbonyl groups and ether groups, for example, have absorption peaks, and so ultraviolet-region absorbance detectors have a potential to be a detector having universal responsivity, and so have been studied repeatedly so far. Such an ultraviolet-region absorbance detector, however, has a problem that its baseline changes greatly when a gradient analysis is applied in the liquid chromatographic field, thus failing to yield a good chromatogram. The gradient analysis is a method of successively changing the concentration of the mobile phase from aqueous solution to organic-solvent based solution such as methanol or acetonitrile. Since such an organic solvent has a strong absorption in the ultraviolet wavelength band compared with water, the baseline changes with the change in composition ratio of the organic solvent during a gradient analysis, and so the applicable range thereof is limited.
To solve this problem, the following correction method has been proposed (Patent Document 1). Firstly, a blank sample is introduced to acquire a baseline fluctuation value resulting from the mobile phase only. Next, a sample is introduced to acquire a signal fluctuation value resulting from the sample and the mobile phase. Finally, a correction factor is multiplied, and a difference therebetween is calculated, thus reducing a baseline fluctuation resulting from the mobile phase.